P1385: THE GUIDING SIGNIFICANCE OF IMMUNE CELL SUBSET MONITORING IN IMMUNE RECONSTITUTION IN PATIENTS WITH CAR-T BRIDGED ALLOGENEIC HEMATOPOIETIC STEM CELL TRANSPLANTATION
Authors: W. zhao, M. chen, Y. an, P. hu, M. chen, H. Wang, P. Lu, Y. zhao
Journal: HemaSphere (2022)

Background: Immune cell reconstitution after allogeneic hematopoietic stem cell transplantation (allo-HSCT) can effectively prevent infection and graft-versus-leukemia effect. Monitoring the lymphocyte subsets of patients after transplantation has certain guiding value for understanding the immune function status. Aims: study the immune reconstitution after CAR-T bridging HSCT. Methods: A total of 83 patients with acute lymphoblastic leukemia who received allo-HSCT in Beijing Lu Daopei Hospital from August 2018 to December 2021 were included in this study (61 cases of B-ALL and 22 cases of T-ALL,54 males and 29 females) with a median age of 29 years (1-57). 33 were CAR-T patients and 50 were non-CAR-T patients. MFC was applied to detect PB lymphocyte subsets of the patients 1 month before and 1, 2, 3, 6, 8, 10, and 12 months after HSCT, as well as the transplants. Results: Before transplantation, we recorded primary disease CR in 76 cases, PR or NR in 7 cases. The HSCT types are 71 haploids, 6 unrelated donors, and 6 siblings. The difference analysis of pre-transplant status between CAR-T or non-CAR-T groups showed that the CAR-T group had a longer medical history before transplantation than the non-CAR-T group (P=0.000). Furthermore, in the CART group, the serum IgA/IgG/IgM (P= 0.000/0.008/0.000), peripheral blood total lymphocytes, T lymphocytes, helper T cells, cytotoxic T cells, B lymphocytes counts, and other results were lower than those of the non-CAR-T group(P=0.000-0.002). All of the above have significant differences (P<0.05). 2、The difference analysis results of the treatment regimen and immune status between the two groups after transplantation showed that: The dose of rabbit anti-human thymocyte immunoglobulin in the conditioning regimen of the CAR-T group was lower than that of the non-CAR-T group (P=0.023);The CD34+ count in the reinfused graft was higher than that in the non-CAR-T group (P=0.003);The leukocyte/neutrophil engraftment time was earlier in the CAR-T group after transplantation (P=0.038/0.043) and the plasma cytomegalovirus DNA level was higher (P=0.002), the application time of cyclosporine was significantly shorter than that of the non-CAR-T group (P=0.000). 3、The difference analysis of the results of peripheral blood immune cell subsets between the two groups at 1, 2, 3, 6, 8, 10, and 12 months after transplantation showed that: There were no significant differences in the detection results of total lymphocytes, T lymphocytes cells, helper T cells, cytotoxic T cells, B lymphocytes, NK and NKT cells, and CD4/CD8 ratio (P>0.05). Furthermore, there were no significant differences in other biomarkers. Image:Summary/Conclusion: For CAR-T patients with low immune function before transplantation, to achieve the same immune reconstitution level as non-CAR-T patients, we reduced the dose of ATG in the conditioning regimen, increased the CD34+ reinfusion count of the graft, and stopped cyclosporine as soon as possible after transplantation. Dynamic monitoring of immune cell subsets in peripheral blood of patients after transplantation helps grasp the status of postoperative immune function and immune reconstitution and guides clinical treatment.